Low-carbohydrate diets may increase the risk of people suffering bowel cancer, scientists have claimed.

Researchers from Aberdeen's Rowett Research Institute believe there is a link between eating less carbohydrate and reducing cancer-fighting bacteria.

The Rowett study saw 19 overweight men given three diets containing different levels of carbohydrate.

Low-carbohydrate diets, such as Atkins, have their critics, however supporters say studies have shown effectiveness.

In the long run, it is possible that such diets could contribute to colorectal cancer

Prof Harry FlintRowett Research Institute

The researchers said they had discovered a link between consuming carbohydrate and the production of a fatty acid in the gut that protects against colorectal cancer.

The acid, called butyrate, is produced by bacteria and helps kill off cancerous cells.

The researchers said they found low-carbohydrate regimes could cause a four-fold reduction in the cancer-fighting bacteria.

The diets start by reducing carbohydrate intake, including foods such as potatoes and bread.

The researchers said the danger comes if dieters are tempted to keep the level low.

'Preventable disease'

They said the study showed a low carbohydrate group consuming only 24g a day - behind the high intake group at 400g - saw a four-fold drop in the level of the cancer-fighting bacteria.

Prof Harry Flint, who led the research, said: "In the long run, it is possible that such diets could contribute to colorectal cancer.

"It is a preventable disease, and there is evidence that poor diet can increase your risk."

He said it was likely the results would be the same in women.

Professor Annie Anderson, Dundee-based nutritional adviser to Bowel Cancer UK, said: "Compared to other low fat diets, there is little merit in low carbohydrate diets, apart for the fact that that they can help people to lose weight.

"There are no long term benefits to cutting down on fruits and fibre, for example, in bread, and as this report shows, doing so is likely to have a negative impact on your bowel health and may increase your risk of bowel cancer."